The invention relates to the production of filter materials with high absorbing and filtering properties, especially relating to the production of filter materials based on synthetic polymeric fibers for fine purification and disinfecting of water, water solutions and other liquids, and it also can be used in medicine and microbiology for sterilizing filtration of injections and other solutions, for the concentration of biomolecules in physiological liquids, for the concentration and extraction of viruses, for apyrogenic water preparation, and in biocatalytic membrane reactors.
There are nonwoven materials made of thin polymeric fibers, prepared by the electrospinning method, the so-called Petryanov fabrics (filters), designed for gas and liquid filtration, bacterial gas purification [High-performance gas cleaning from aerosols with Petryanov filters/P. I. Basmanov, V. I. Kirichenko, Y. N. Filatov, Y. L. Yurov; ex. ed. V. I. Kirichenko. —Moscow: Science, 2003. -271 p.]
The properties of these materials are based on the adhesion of admixture particles in liquid and gas on the filter fibers at their collision. However, they are inefficient in water purification from pathogenic flora due to the weak adhesion of microorganisms to filter fibers in aqueous medium.
There is a method of adsorbent production [RU 2075345 C1, 1997], where ultrafine aluminum powder with specific surface area ranging from 5 to 20 m2/g, produced by electrical explosion of aluminum wire in argon medium, is treated with water at a temperature from 50 to 60° C. followed by heating at a temperature from 300 to 500° C. during 1 or 3 hours.
The adsorbent based on ultrafine aluminum oxide provides high sorption capacity relative to water-soluble mineral oils, phenols and heavy metals.
There is a method of adsorbents production [RU 2168357 C2, 2001] based on oxide materials, where ultrafine aluminum powder with specific surface area ranging from 5 to 20 m2/g, produced by electrical explosion of aluminum wire in argon, is treated with water at a temperature from 50 to 60° C., heated at a temperature from 200 to 300° C. during 1 or 3 hours, refluxed in saturated sodium bicarbonate solution during 0.5 or 1.5 hours followed by reheating at a temperature from 200 to 300° C.
This method improves the powder absorbability relative to phenols, heavy metals and halogens without capacity loss relative to the water-soluble mineral oils.
There is a method of fine purification of highly-contaminated water [RU 94003073 A, 1995]. The invention is meant for water purification for domestic needs mainly in emergency situations. The aim of the invention is to increase the efficiency of purification process of the highly-contaminated water from mineral oils and mineral contaminations. The gist: highly-contaminated water is sequentially passing through the layer of cellulose, activated by 5% admixture of oxidized atactic polypropylene, through the layer of active aluminum oxide, prepared in the process of ultrafine aluminum powder oxidation in water; with aluminum powder i.e., the product of aluminum wire electrical explosion.
An inorganic adsorbent, i.e., aluminum oxyhydroxide AlOOH (boehmite) with a pore size from 60 to 90 nm subjected to the hydrothermal pretreatment is used for water purification from enteroviruses [SU 1066942 A, 1982] with a particle size from 20 to 30 nm. This method allows achieving 100% purification at concentration of viruses in water ranging from 1.5 to 6.28 lg PFU50/ml and at pH medium being within the limits from 7.0 to 7.5.
The disadvantage of this method is the required prolonged contact (from 2 to 6 hours) of viruliferous water with an adsorbent.
Application of water purification method, described in [RU 94003073 A, 1995] and adsorbents [RU 2075345 C1, 1997, RU 2168357 C2, 2001] in the form of filter filling requires high pressures applied due to the high hydrodynamic resistance of adsorbent layer. At the same time, there is a carryover of adsorbents by the fluid flow through the filter barriers. Besides, all the methods provide the heating phase of the adsorbent at a temperature from 200 to 300° C. that makes the product more expensive.
There is a method of electropositive sorbent production [U.S. Pat. No. 6,838,005 B1, 2005], which comprises the mixing of nonspherical aluminum oxide particles or aluminum source, which then reacts with water solution thus generating the nonspherical aluminum oxide particles with the second solid component, i.e., particles of fibrous material. The filter material is mould of this composite using the “paper” technology.
There is a sorbent, which consists of nonspherical aluminum oxide particles and particles of fibrous material and includes a component with a surface negative charge and modifying composition, chosen from the row of magnesium oxide or magnesium hydroxide, silicon or their mixture [RU 2242276 C1, 2004]. The method of sorbent production comprises the mixing of nonspherical aluminum oxide particles with the fibrous material particles. Before mixing, the component with a surface negative charge is added to the fibrous material. After these three components being mixed, the modifying composition is added to the mixture. Besides, in the process of mixing of the first three components, the mixture activation is conducted by electric current or ultrasound. Then the filter material is mould of this composite using the “paper” technology.
The main disadvantage of the above-mentioned sorbents is the using of micron glass fiber [U.S. Pat. No. 6,838,005 B1, 2005] and cellulose [RU 2242276 C1, 2004] as a fiber base. Glass fiber can be harmful if its particles penetrate into the filtered liquid, and cellulose is a nutrient medium for bacteria and unwanted in filters of long-term usage. Besides, the formation of filter materials using the “paper making” technology restricts the range of materials, which can be used as the second solid component (fibrous base), because all the mixture components for this formation are used as a suspension of single small particles. When the fibers made of polymeric materials with a diameter, less than 2 μm are used, it is difficult to get a mechanically strong material using the “paper making” technology. At the same time, just these materials have the qualities, preferable at production of filter materials.
A considerable disadvantage of this sorbent production method [RU 2242276 C1, 2004] is the necessity of mixture activation by electric current or ultrasound that makes the sorbent production technology more expensive and complicated.
There is a method of filter element modification [RU 2135262 C1, 1999], which involves the workpiece impregnation of the filter element, formed of carbonic nonwoven fabric, referring to the synthetic polymeric materials, by the modifying composition. The modifying composition represents water-organic solution of the nanostructured silver particles. A filter element, produced by this method, allows filtering out microbiological admixtures from water.
As it is defined in the description, after the carbon fiber material being treated by silver solution, there are, at least, one hundred viable bacterial cells less left in the filtrate as compared with the used untreated material. This is due to the silver antibacterial properties, but at the same time, there are toxins penetrating into the filtrate, generated as a result of microorganisms' death. The impoverishment of bacterial cells by one hundred is insufficient, when there is a high concentration of microorganisms in the original liquid, e.g., 104 CFU/ml.
Besides, carbon fiber is a very expensive material.